(Bouzu nikukerya kesa made nikui;
“If you hate a priest, even the priestly robe is loathsome”)
If you hate somebody or something, then all too often you also start to dislike neutral things that you associate with the object of your dislike. If you hate a Buddhist priest (or priests in general), then you may begin to have a negative reaction even to their distinctive clothing.
We begin with the noun 坊主 (bouzu), a relatively casual term for a Buddhist priest. Next we have the adjective 憎い (nikui), “detestable.” (While modern Japanese might put a particle such as subject-marker が (ga) in between noun and adjective, this is elided here.) The adjective appears in imperfective form as 憎け (nikuke). Technically what follows is passive-marker postpositional る (ru), also in imperfective form as れ (re), and then hypothetical-marker postpositional ば (ba), “if.” However, all this is slurred together and comes out as りゃ (rya), continuing the casual mode of speech from 坊主.
The following independent clause begins with the noun 袈裟 (kesa), a “kasaya,” a traditional outfit worn by Buddhist priests. This is marked by the particle まで (made), often “up to” or “until,” but here probably best rendered as “even.” And finally we have the adjective 憎い again, this time in conclusive form.
It’s less common, but perfectly acceptable, to replace the ~けりゃ conjugation with the more correct ければ, and/or to use the older conclusive form 憎し at the end. One variant phrase replaces 坊主 with the more formal 法師 (houshi), also indicating a Buddhist priest but literally meaning “law teacher.”
Supposedly this phrase carries cultural memories of to Edo-period laws by which people were required to register (and confirm their Buddhist faith) with local temples. While from the government’s point of view this offloaded and organized some bureaucratic work while providing a bulwark against Christian incursions, in practice this placed more power in the hands of priests, that power corrupted, and corruption led to backlash and resentment.
However, note that this saying’s origins go back to the Western Han dynasty in China, specifically a collection of stories known as the Shuo Yuan (Japanese 『説苑』= Zeien).
(“Tsuittaa de ano sakka no momegoto ni makikomarete kara, kare no hon mo iya ni natte yomenaku natta. Bouzu nikukerya kesa made, ka.”)
[“Ever since I got caught up in that one author’s Twitter war, even his books make me feel awful; I can’t read them any more. Even the priest’s robe, I guess.”]